Telling a few white lies may seem harmless, but a new study suggests that you might improve your mental and physical health if you cut down on the fibs you tell.

“We found that the participants could purposefully and dramatically reduce their everyday lies, and that in turn was associated with significantly improved health,” said Anita Kelly, study author and professor of psychology at the University of Notre Dame, in a statement. Kelly presented her findings at the annual meeting of the American Psychological Association in Orlando.

For her study, Kelly recruited 110 adults and asked half of them to stop lying for 10 weeks. Lies included big ones and tiny ones — any false statement — but participants were still allowed to do things like omit the truth, keep secrets and dodge questions they didn’t want to answer. The other half of the participants weren’t given any special instructions about lying, except that they had to report the number of lies they told each week. The participants, aged 18 to 71, took a weekly lie detector test and filled out questionnaires about their physical and mental health as well as the quality of their relationships.

It turns out that both groups reduced their lying, but those who were specifically told to tell the truth fibbed less — and improved their health more. For example, when participants in the no-lie group told three fewer minor lies a week, they reported four fewer mental-health complaints (such as feeling sad or stressed) and three fewer physical complaints (such as headaches or sore throats). Those in the control group who independently told fewer lies logged fewer health complaints as well, but only by two or three complaints.

On average, Americans tell about 11 lies a week, the authors report. By the end of their 10-week study period, participants in the no-lie group were down to one lie a week. The comparison group was telling more than three lies a week, down from an average of six at the start of the study.

People really took the task to heart, the researchers found: participants found themselves being honest about their daily accomplishments instead of exaggerating them, for example, and they stopped making up excuses for being late or failing to complete a task. They also came up with strategies to avoid lying, such as responding to tough questions with another question in order to distract the other person.

In addition to improving their mental and physical health, the truth-tellers said that their close personal relationships had also improved and that their other social interactions had been easier.

“I think lying can cause a lot of stress for people, contributing to anxiety and even depression,” Dr. Bryan Bruno, acting chairman of the department of psychiatry at Lenox Hill Hospital in New York City, told HealthDay. “Lying less is not only good for your relationships, but for yourself as an individual. People might recognize the more devastating impact lying can have on relationships, but probably don’t recognize the extent to which it can cause a lot of internal stress.”